In this study, ReNuMa was applied to stimulate the non-point source pollution loading of total nitrogen in the upstream watershed of the Shitoukoumen Reservoir, which is the most important drinking water source of Changchun. Temporal and spatial distributions of non-point TN pollution have been calculated and analyzed quantificationally through the investigation and simulation. On the temporal scales, TN loading during the rainy seasons accounted for 69%. At the spatial scales, the watershed of Yinma River had the highest ratio of TN loading to the total and farmlands contribute the highest NPS loading.